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Evaluation of Notional Loads Magnitude to Three Calibration Moment Resisting Frames subjected to Indonesian Seismic Load

Abstract—AISC 2010 has been adopted on Indonesian steel design code since 2015. AISC 2010 uses Direct Analysis Method (DAM) for steel structural stability where it substitutes Effective Length Method (ELM). DAM is a second order elastic analysis, allows a more accurate determination of the load effects in the structure through the inclusion of the effects of geometric imperfections and stiffness reductions directly within the structural analysis. Notional load as 2 per mill of gravity load should be applied horizontally to represent geometric imperfection of 1/500L. It is allowed to adjust the notional load coefficient proportionally based on a nominal initial story out-of-plumbness ratio. Results from three different calibration frames from previous research which are considered as advanced analysis were used as references. Through numerical simulation by using SAP software, the advanced analysis considered as a second order inelastic method enabling to accommodate the real collapse mechanism of structure will be validated through three calibration frames. Evaluation studies were first conducted to compare ELM and DAM effectiveness, and later to find out the appropriate magnitude of notional load on steel moment resisting frame subjected to Indonesian Seismic Load. The calibration frames consisted of one story, 3-stories and 6-stories were reanalyzed with four different methods: ELM first order analysis, ELM second order analysis, DAM with different notional loads coefficient as 0.002 and 0.003; and Response Spectrum taking into account the two different notional loads coefficients. Indonesian seismic load in three seismic zones with three different soil conditions were considered. The results were compared to advanced analysis. It is found that DAM has the closest result to advanced analysis and notional load coefficient of 0.003 reveals as the most appropriate value considered from its base shear-drift curve, P-M interaction and drift.

Index Terms—effective length method, direct analysis method, response spectrum, moment resisting frames, calibration frame